This application is based on German Application DE 100 21 515.7, filed May 3, 2000, which disclosure is incorporated herein by reference.
The present invention relates to a process for the preparation of alkaline earth salts of D-pantothenic acid from fermentation broths.
Pantothenic acid is a commercially important vitamin that is used in cosmetics, medicine, human nutrition and in animal nutrition.
Pantothenic acid can be prepared by chemical synthesis or via biotechnology by fermentation of suitable microorganisms in suitable nutrient solutions. DL-pantolactone is an important compound in the chemical synthesis, and is prepared in a multi-stage process from formaldehyde, isobutyl aldehyde and cyanide. In further process steps the racemic mixture is separated and D-pantolactone is condensed with xcex2-alanine to yield D-pantothenic acid.
The advantage of a fermentative preparation using microorganisms is the direct formation of the correct stereoisometric form, namely the D-form of pantothenic acid free from L-pantothenic acid.
Various types of bacteria, for example Escherichia coli, Arthrobacter ureafaciens, Corynebacterium erythrogenes, Brevibacterium ammoniagenes and also yeasts, for example Debaromyces castellii may, as demonstrated in EP-A-0 493 060, EP-A-0 590 857 and WO 97/10340, produce D-pantothenic acid under suitable fermentation conditions. Particularly suitable microorganisms are the derivatives, described in the citations, of Escherichia coli IF03547, for example the strains FV5069/pFV31 or FV5069/pFV202.
In the fermentative preparation of D-pantothenic acid as is described in EP-A-0 493 060, EP-A-0 590 857 and WO 97/10340, a microorganism capable of producing D-pantothenic acid is cultivated in a suitable nutrient medium and the D-pantothenic acid that is formed is then isolated according to a complicated expensive procedure, purified, and obtained as the calcium salt.
Suitable nutrient media contain a carbon source such as glucose or starch flour hydrolyzate, precursors such as xcex2-alanine, D,L-pantoic acid or D,L-pantolactone, a nitrogen source such as ammonium sulfate, a phosphorus source such as potassium phosphate, and further salts, trace elements, amino acids and vitamins, and optionally complex media additives such as yeast extract or corn steep liquor. The microorganisms are then incubated in this medium at a suitable pH value under appropriate aeration and stirring, whereupon the microorganisms form D-pantothenic acid.
EP-A-0 590 857 describes, for example, a fed batch process for preparing pantothenic acid in a 5 liter reactor filled with 2.3 liter or 2.5 liter of culture medium. In this experimental example, solid calcium carbonate was added presumably to regulate the pH. The preliminary addition or subsequent addition of solid calcium carbonate is however extremely undesirable in a large-scale reactor having a volume of many cubic meters, because the material loading is increased by the calcium carbonate deposits on the stirrer blades, internal surfaces and seals, and the flow properties of the culture liquid and the sterile conditions are adversely affected.
According to the present prior art, which is outlined in W096/33283 and EP-A-0 590857, the calcium salt of D-pantothenic acid is obtained by a complicated and costly isolation and purification process starting from a fermentation broth containing pantothenic acid. After a first separation of the biomass by filtration or centrifugation, the filtrate is worked up further by purification by means of activated charcoal or by column chromatography. After adding calcium hydroxide to the pretreated filtrate or eluate, the batch is then purified by crystallization.
The purification method described in W096/33283 is carried out as follows. The filtrate is decolorized by means of activated charcoal in a first column. The pH is adjusted to 3.0 with concentrated hydrochloric acid and the liquid is then purified continuously through two columns packed with activated charcoal. The elution of the D-pantothenic acid is performed with methyl alcohol. A subsequent neutralization is carried out with Ca(OH)2 powder while thoroughly mixing. The calcium D-pantothenate is obtained by subsequent crystallization at 5xc2x0 C.
The purification method described in EP-A 0 590 857 is carried out as follows. The filtrate is first of all purified with the aid of cation exchange and anion exchange columns. Elution is performed with hydrochloric acid. The eluted fraction is then neutralized with Ca(OH)2, following which activated charcoal is added and the mixture is filtered. The resultant filtrate is extracted in a low molecular weight alcohol (methanol, ethanol, isopropanol) and the calcium D-pantothenate is obtained by crystallization.
The calcium D-pantothenate prepared in the aforementioned manner is used as a feed additive for animal nutrition.
An improved process for preparing alkaline earth salts, in particular the calcium and magnesium salts, of D-pantothenic acid, which are suitable for use as feed additives in animal nutrition, is provided.
The vitamin D-pantothenic acid is a commercially important product that is used in animal nutrition, medicine, human nutrition and in cosmetics. There is, therefore, a general interest in providing new processes for preparing pantothenic acid or its salts.
The present invention provides a process for preparing alkaline earth salts of D-pantothenic acid or mixtures containing the latter, from fermentation broths, which is characterized in that
(a) the fermentation is carried out in the presence of alkaline earth compound,
(b) after completion of the fermentation the biomass is optionally removed either in whole or in part,
(c) the thus worked up fermentation broth is concentrated, and
(d) the alkaline earth salt or salts of D-pantothenic acid is/are obtained from the latter in pure form or as a mixture containing the constituents of the fermentation broth.
The present invention also provides a process which is characterized in that one or more alkaline earth salt(s) of D-pantothenic acid is/are added in the desired amount to the constituents of the fermentation broth and mixture containing one or more of the alkaline earth salts of D-pantothenic acid.
The invention furthermore provides a process for preparing alkaline earth salts of D-pantothenic acid, characterized in that
a) the biomass is separated from a fermentation broth containing alkaline earth salt(s) of D-pantothenic acid,
b) the cell-free fermentation broth is concentrated,
c) a hydrophilic organic solvent, in particular ethanol, methanol or acetone, is added to the concentrate thus obtained, following which
d) the alkaline earth salt(s) of pantothenic acid is/are isolated, optionally washed with a hydrophilic organic solvent and then, if desired,
e) recrystallized in an aqueous solution of a hydrophilic organic solvent, optionally with the addition of activated charcoal, and obtained in a high state of purity.
All microorganisms that are capable of producing D-pantothenic acid and which produce D-pantothenic acid under appropriate fermentation conditions are suitable for the process according to the invention. The microorganisms can produce pantothenic acid from glucose, sucrose, lactose, fructose, maltose, molasses, starch, cellulose or from glycerol and ethanol.
The microorganisms may be fungi or yeasts, for example Debaromyces castells or Saccharomyces cerevisiae or Gram-positive bacteria, for example of the genus Corynebacterium or may be Gram-negative bacteria, for example of the family of Enterobacteriaceae. Within the family of Enterobacteriaceae, the genus Escherichia as exemplified by the type Escherichia coli, in particular, should be mentioned. Within the type Escherichia coli there should be mentioned the so-called K-12 strains, for example the strains MG1655 or W3110 (Neidhard et al.: Escherichia coli and Salmonella. Cellular and Molecular Biology (ASM Press, Washington D.C.)) or the Escherichia coli wild type strain IF03547 (Institute for Fermentation, Osaka, Japan) and mutants derived therefrom. Among the strains obtained from IF03547, there should in turn be mentioned FV5069/pFV31 (EP-A-0 590 857, U.S. Pat. No. 5,518,906) and FV5069/pFV202 (WO 97/10340, U.S. Pat. No. 5,932,457). In the genus Corynebacterium the type Corynebacterium glutamicum should be mentioned in particular.
The aforementioned microorganisms may be cultivated continuously or discontinuously in a batch process or in a fed batch or repeated fed batch process in order to produce alkaline earth salts of D-pantothenic acid. A summary of known cultivation methods is described in the handbook by Chmiel (Bioprozesstechnik 1. Einfxc3xchrung in die Bioverfahrenstechnik [introduction to Biotechnology](Gustav Fischer Verlag, Stuttgart, 1991)) or in the handbook by Storhas (Bioreaktoren und periphere Einrichtungen (Vieweg Verlag, Brunswick/Wiesbaden, 1994)).
The culture medium to be used must suitably satisfy the requirements of the relevant microorganisms. Descriptions of culture media for various microorganisms are contained in the handbook xe2x80x9cManual of Methods for General Bacteriologyxe2x80x9d of the American Society for Bacteriology (Washington D.C., USA, 1981). Sugars and carbohydrates, for example glucose, sucrose, lactose, fructose, maltose, molasses, starch and cellulose, oils and fats such as soya bean oil, sunflower oil, groundnut oil and coconut oil, fatty acids, for example palmitic acid, stearic acid and linoleic acid, alcohols such as glycerol and ethanol, and also organic acids such as acetic acid may be used as sources of carbon. These substances may be used individually or as a mixture. Examples of nitrogen sources that may be used are organic nitrogen-containing compounds, such as peptones, yeast extract, meat extract, malt extract, corn steep liquor, soya bean flour and urea, or inorganic compounds such as ammonium sulfate, ammonium chloride, ammonium phosphate, ammonium carbonate and ammonium nitrate. The nitrogen sources may be used individually or as a mixture. Phosphorus sources may be potassium dihydrogen phosphate or dipotassium hydrogen phosphate or the corresponding sodium-containing salts. The culture medium must also contain metal salts such as magnesium sulfate or iron sulfate that are necessary for growth. Finally, essential growth factors such as amino acids and vitamins may additionally be used together with the aforementioned substances. Precursors such as xcex2-alanine or optionally their salts may furthermore be added to the culture medium. The aforementioned substances may be added to the culture in the form of a single addition or may be appropriately metered in during the cultivation.
Basic compounds such as ammonia or ammonia water or acidic compounds such as phosphoric acid or sulfuric acid may be used in an appropriate manner to control the pH of the culture, insofar as the process according to the invention does not involve any other measures. Anti-foaming agents such as fatty acid polyglycol esters may be used to control foam formation. Suitable selectively acting substances, for example antibiotics, may be added to maintain the stability of plasmids. Oxygen or oxygen-containing gas mixtures, for example air, are introduced into the culture in order to maintain aerobic conditions. The temperature of the culture is normally 20xc2x0 C. to 50xc2x0 C., and preferably 25xc2x0 C. to 45xc2x0 C. Cultivation is continued until a maximum amount of D-pantothenic acid has been formed. This objective is normally achieved within 10 hours to 160 hours.
It has been found that the alkaline earth salts, in particular the calcium salt and magnesium salt of D-pantothenic acid, can be produced in a simple manner by adding during the fermentation a solution or suspension of an alkaline earth-containing inorganic compound, such as for example calcium hydroxide or magnesium hydroxide, preferably calcium hydroxide or magnesium oxide, or also an alkaline earth salt of an organic acid, for example calcium acetate, calcium fumarate or calcium aspartate, continuously to the fermentation. It is also possible to meter in the alkaline earth-containing compound batchwise. In this way the cation necessary for forming the desired alkaline earth salt of D-pantothenic acid is introduced directly into the fermentation broth.
The fermentation process according to the invention is generally characterized in that a microorganism capable of producing D-pantothenic acid is first of all cultivated in a known manner using ammonia as pH regulator and nitrogen source, and in the following production stage the pH is preferably adjusted by using a solution or suspension of an alkaline earth-containing compound, for example calcium hydroxide, magnesium hydroxide, magnesium oxide, calcium acetate, calcium fumarate or calcium aspartate. If calcium salts of organic acids are used, the organic radicals are generally utilized as a carbon source by the microorganisms.
The solutions or suspensions of the alkaline earth-containing compounds that are used, in particular calcium hydroxide and magnesium hydroxide, have a concentration of 5-50 wt. %, preferably 5-30 wt. %, the range from 10-25 wt. % being most particularly preferred. It is also possible, according to the invention, to employ mixtures of various alkaline earth-containing compounds in these concentration ranges.
The alkaline earth compound is metered into the fermentation broth in such a way that the molar ratio of alkaline earth compound to the formed D-pantothenic acid is in the range 1:0.5 to 1:20, preferably in the range 1:1.3 to 1:10, more preferably in the range 1:1.3 to 1:2.5, the stoichiometric range from 1:1.8 to 1:2.2 being most particularly preferred. If necessary, the pH can be adjusted during the course of the fermentation by metering in ammonia in aqueous form or as a gas, should an excessive formation of byproducts containing carboxyl groups occur, in order to maintain the ratio of alkaline earth compound to formed D-pantothenic acid within the desired range.
The metering in of the alkaline earth compound may take place after a fermentation time of 1-70 hours, preferably 10-40 hours and most preferably 20-25 hours. The concentration of D-pantothenic acid at the start of the metering in of the alkaline earth compound is generally 0.5-70 g/liter, preferably 5-35 g/liter and particularly preferably 20-25 g/liter. The concentration of biomass at the time the alkaline earth compound is metered in is generally 1-30 g dry weight/liter, preferably 10-23 g dry weight/liter and particularly preferably 17-21 g dry weight/liter.
The invention also provides a process for producing powders or feed additives containing alkaline earth salts, in particular the calcium or magnesium salts of D-pantothenic acid, in a quick and cost-effective manner. To this end a fermentation broth prepared according to the process of the invention and containing in particular calcium or magnesium D-pantothenate is concentrated using known methods, for example with the aid of a rotary evaporator, thin-film evaporator or falling-film evaporator. The fermentation broth that has been concentrated in this way is then converted by spray drying or freeze drying techniques, such as are described for example in the handbook by M. L. Shuler and F. Kargi xe2x80x9cBioprocess Engineering, Basic Conceptsxe2x80x9d (Prentice Hall Inc., Englewood Cliffs, N.J., USA, 1992), or by other appropriate methods, into a preferably free-flowing powder or feed additive. A substance or preparation containing calcium or magnesium D-pantothenate may optionally be added at a suitable process stage in order to achieve a desired concentration level. The concentration of calcium or magnesium D-pantothenatexe2x80x94expressed as D-pantothenic acidxe2x80x94in the resultant product is 20 to 80 wt. %, preferably 30 to 75 wt. %. The product is suitable as a feed additive for use in animal nutrition.
The invention also provides a further method of producing powders or feed additives containing calcium or magnesium D-pantothenate. To this end a fermentation broth prepared as described above and containing, in particular, calcium or magnesium D-pantothenate is first freed either completely or partially from the biomass by known separation methods, for example centrifugation, filtration, decanting or a combination thereof. The cell-free fermentation broth is then concentrated using known methods, for example with the aid of a rotary evaporator, thin-film evaporator or falling-film evaporator. The suspension concentrated in this manner is then worked up by methods involving spray drying or freeze drying or by other suitable processes into a preferably free flowing powder. A substance or preparation containing calcium or magnesium D-pantothenate is optionally added at a suitable process stage in order to achieve a desired concentration value. The concentration of calcium or magnesium D-pantothenate, expressed as D-pantothenic acid, in the resultant product is 20 to 80 wt. %, preferably 30 to 75 wt. %. The product is suitable for use as a feed additive in animal nutrition.
The invention likewise provides a method for producing crystals containing calcium or magnesium D-pantothenate in a quick and cost-effective manner. To this end a fermentation broth prepared as described above and containing calcium or magnesium D-pantothenate is first of all freed as described above from the biomass. The cell-free fermentation broth is then concentrated using known methods, for example with the aid of a rotary evaporator, thin-film evaporator or falling-film evaporator. A hydrophilic, organic solvent, for example ethanol, methanol or acetone is then added to the suspension that has been concentrated in this way. Residual solid material is precipitated out by cooling the suspension to 0-8xc2x0 C., preferably 0-5xc2x0 C. The desired salt is then crystallized by inoculating with crystalline calcium or magnesium D-pantothenate or substances containing crystalline calcium or magnesium D-pantothenate. The crystallization takes place at 0-8xc2x0 C., preferably 0-5xc2x0 C., and lasts from 1 hour to 12 days, preferably 1 hour to 10 days, and particularly preferably 1 hour to 8 days. The crystalline crop obtained in this way is preferably washed with methanol and then dried. If a product of higher purity is required, the crystalline crop is taken up in a water-containing solution of methanol and is crystallized, optionally under the addition of activated charcoal. The water-containing solution of methanol has a methanol content of 70 to 99 vol. %, preferably 80 to 99 vol. %, and particularly preferably 90 to 99 vol. %.
The concentration of calcium or magnesium D-pantothenate in the crystalline product obtained in this way is 60 to 99 wt. %, preferably 70 to 99 wt. %, and particularly preferably 80 to 99 wt. %. The product is suitable for use as a feed additive in animal nutrition.
The concentration of D-pantothenic acid may be determined by known methods (Velisek; Chromatographic Science 60, 515-560 (1992)). Pure calcium D-pantothenate ( greater than 99 wt. %) has a content of 91.16 wt. % D-pantothenic acid. Pure magnesium D-pantothenate ( greater than 99 wt. %) has a content of 94.73 wt. % D-pantothenic acid.